This invention relates to a camshaft arrangement for a multi-valve engine and more particularly to an improved, compact valve operating system for a multiple valve internal combustion engine operated by a single overhead mounted camshaft.
The advantages of multiple valve internal combustion engines are well known. Briefly, stated, the use of multiple valves for supplying either or both intake charge to the combustion chamber and for discharging the exhaust charge from the combustion chamber permits a greater effective flow area with lower reciprocating masses. Although the use of multiple valves and their advantages are well known, there have been a number of factors which have prevented the wider adoption of such multiple valve arrangements to internal combustion engines. One of the obstacles to the adoption of multiple valve engines has been the complexity of the arrangement for operating such multiple valves. Normally, it has been the practice to employ at least two camshafts for each cylinder or cylinder bank in order to operate the multiple valves. The addition of such a number of camshafts, obviously, gives rise to increased engine cost and also complexity.
Although some of these disadvantages can be overcome through the use of a single camshaft operating all of the valves, it has been difficult to provide a single camshaft arrangement for operating such multiple valves. When a single camshaft is employed for operating multiple valves, the camshaft has generally a greater number of lobes than are required when the intake valves and exhaust valves are each operated by a single camshaft. In addition, it is desirable to maintain the engine as compact as possible, and at times this has not been possible with the use of a single camshaft, although it would on the surface appear to be possible to do so. The reason for the complexity is the number of rocker arms that are required to operate all of the valves and, furthermore, the necessity to provide adequate support for the camshaft.
When a single camshaft is employed for operating multiple valves, the loading on the camshaft becomes quite high. Therefore, it is necessary to provide adequate bearing support for the camshaft so as to avoid its flexure. However, previous proposed arrangements for this purpose have not been completely satisfactory.
It is, therefore, a principal object of this invention to provide an improved valve operating mechanism for a multiple valve internal combustion engine.
It is another object of this invention to provide an improved arrangement for operating multiple valves of an internal combustion engine from a single camshaft.
It is a further object of this invention to provide a camshaft arrangement for operating multiple valves of a single cylinder or cylinder bank and wherein the camshaft is provided with adequate and well placed bearing support.